Vapor barrier for use in buildings

ABSTRACT

A vapor barrier for use in buildings, in particular for use in facades and/or in the rehabilitation of building roofs, wherein the barrier has a water vapor diffusion resistance (s d  factor) of 0.4 to 1.9 m diffusion-equivalent air layer thickness which is constant over the entire surface area.

The invention relates to a vapor barrier for use in buildings, in particular for the use in facades and/or in the rehabilitation of building roofs.

Vapor barriers of the initially mentioned type, especially in the new construction of steep-pitched roofs on the inside of the roof construction, which includes the rafters, a heat-insulating layer preferably arranged between the rafters, a roof underlay arranged on the outer surfaces of the rafters, and a roof covering arranged thereon, are arranged on the inside surfaces of the rafters and on the heat-insulating layer arranged between the rafters.

While the roof underlay arranged under the roof covering and resting on the outer surfaces of the rafters protects the roof construction against exterior influences, in particular against the introduction of detrimental humidity from the outside, the vapor barrier is for preventing moisture from being introduced into the roof construction from the interior all year round, since humidity can lead to the formation of detrimental condensate underneath the roof underlay which usually rests on the heat-insulating layer to achieve maximum heat insulation.

To prevent humidity from being transported by convection, the vapor barrier is air-tight. Moreover, the vapor barrier has its water vapor diffusion resistance adapted, to avoid the formation of detrimental condensate on the outside, underneath the roof underlay, which, among other things, can result in the heat-insulating layer being damaged.

In the construction of new roofs, vapor barriers of the initially mentioned type can be installed in a simple manner as a large surface area on the undersides of the rafters forming the steep-pitched roof, and bonded in an air-tight manner at the edges and in the overlapping area. In the rehabilitation of existing building roofs, which usually becomes necessary because the roof covering needs renewing, it usually makes sense to also renew the heat-insulation, the roof underlay and the vapor barrier, since the buildings to be rehabilitated usually no longer fulfill the current building regulations. There is, however, a problem in that usually the interior cladding of the rooms on the inside of the steep-pitched roof should be preserved. This is why it is possible to install a vapor barrier only from the outside of the steep-pitched roof.

However, to be able to install in the case of rehabilitation the vapor barrier without gaps, and therefore in an air-tight manner, it must be wrapped round the outside of the rafters in a looped fashion after removing the roof covering and any existing old heat insulation between the rafters, since it is not possible to achieve a reliable air-tight fit of the individual vapor barrier webs on the sides of the rafters.

When the vapor barrier is wrapped round the outside of the rafters in a looped fashion, as seen in cross-section, it is arranged so that it extends on the side surface of the rafter until it reaches the back of the interior cladding to be preserved, then in contact with the latter until it reaches the next rafter, and then upwards round the outside of the rafter and down again until it reaches the next rafter space.

This method of installation has a drawback, however, in that condensate forms, in particular in winter, underneath the vapor barriers conventionally installed round the outside of the rafters, since they have a high diffusion resistance, as normally used in the construction of new buildings. For the rehabilitation of steep-pitched roofs in the above-described manner, these vapor barriers are unsuitable, however, because there is a possibility that humidity will accumulate within the rafter, and mould may form, if the humidity dissipation is not sufficient.

To obviate this, the vapor barrier must be as permeable to diffusion as possible, at least in the area on the top surface of the rafters. Such a vapor barrier which is permeable to diffusion would result, however, in the overall diffusion resistance being too low due to the usually present inside cladding of stucco-covered wood wool lightweight building board or slatted ceilings in the area of the rafter space, i.e. in the area between the rafters, which would allow detrimental condensate to form in the area of the heat insulation or underneath the roof underlay.

To solve this problem, a vapor barrier is known from the state of the art according to EP 0 821 755 having an s_(d) factor which varies in response to water absorption and water dissipation. When condensate forms on the surface of the vapor barrier, the molecular structure changes so that the s_(d) factor is lowered to a value of at most 0.2 m of equivalent air layer thickness. The amount of condensate water underneath the vapor barrier will then be able to disappear to the outside in the course of time and when heated from the outside through the meanwhile vapor-permeable foil.

This moisture-adaptive vapor barrier has a drawback, however, in that due to its function the timber moisture may exceed the critical value of 18%, where mould growth is to be expected over a certain amount of time. Moreover, the polyamide raw material necessary for the manufacture of such vapor barriers, and equivalent raw materials having the requisite properties, are particularly expensive. For example, 60 g/m² of expensive polyamide 6 must be used for the manufacture of a vapor barrier with the values indicated in EP 0 821 755.

Also, when the moisture-adaptive vapor barrier takes up or gives off moisture, the vapor barrier undergoes considerable width and length variations which, depending on the condition of the vapor barrier during installation, leads to crinkling with possible leaks in the area of overlaps and seams, or to shrinking of the vapor barrier, wherein the latter may be destroyed in the extreme case, in particular when the vapor barrier is combined with an incompressible heat insulation. The shrinking of the vapor barrier, when a compressible heat insulation is used, in any case, however, leads to the formation of heat leaks due to the formation of hollow gaps in which air can circulate.

Moreover, the moisture-adaptive vapor barrier cannot be used in areas above rooms with constant high air humidity, since the diffusion resistance adjusted at the vapor barrier would constantly be too low.

Another rehabilitation solution is disclosed by DE 201 20 812. It provides for individual strips of a vapor barrier to be installed in parallel to the rafters, wherein diffusion-permeable and diffusion-tight vapor barriers alternate in such a way that the diffusion-permeable strips rest on the rafter and surround it, and the diffusion-tight strips are arranged between the rafters and rest on the interior cladding. Adhesive tape is used to form the air-tight bond. A particular drawback with this solution lies in the difficult installation and the overall higher installation effort as against an integral vapor barrier. Moreover, the diffusion-tight strips always have to be sized to the existing rafter spaces which can vary widely, in particular in old buildings.

From DE 196 51 843, an integral vapor barrier is known, which is also installed in parallel to the rafters and has connected areas, each having different diffusion resistances. However, such a vapor barrier has a drawback in that it cannot be adapted to varying rafter spaces. It can therefore only be used in new buildings where constant rafter spaces are the rule.

Vapor barriers for the rehabilitation of old roofs are also commercially available having a constant s_(d) factor of at least 2 m. They are a compromise between the requisite water vapor impermeability in the space between rafters and the water vapor permeability in the area of the rafters, and can be easily installed. An s_(d) factor of at least 2 m is indicated as the absolute minimum in the state of the art in order to avoid the formation of condensate on the underside of the roof underlay.

The drawback of this approach is that the limit value of 18% of timber moisture is usually exceeded so that mould may grow. In particular, when the rafters are not particularly high, which is often the case with old buildings, there is a very high risk that the timber moisture of 18% is constantly exceeded. This results from the fact that wood by itself has a resistance against vapor pressure. If the rafter thickness is small, the resistance is considerably less, which results in substantial timber moisture.

It is therefore an object of the present invention to provide a vapor barrier which is suitable in particular for the rehabilitation of building roofs which are only accessible from the outside, is easy to install, and obviates the detrimental formation of condensate in the area above the vapor barrier and the detrimental rise in the timber moisture of the rafters.

The present invention solves this problem with a vapor barrier having the features of claim 1. Advantageous embodiments of the vapor barrier are defined in dependent claims 2 to 13.

The vapor barrier according to the present invention is characterized by a water vapor diffusion resistance (s_(d) factor) of between 0.4 and 1.9 m of diffusion-equivalent air layer thickness. All s_(d) factors cited in the context of the present application refer to the DIN 52615 applicable for its determination (attendant conditions: 23° C., o/85% relative moisture).

It has been found surprisingly that, with s_(d) factors in these ranges, both with high initial moistures of structural timber and with interior air at constantly high air moisture levels of 60%, at no time is there a timber moisture which would lead to the rafter being damaged. In particular, the value of 18% timber moisture critical for mould growth is usually no longer exceeded. This is how a cheap vapor barrier may be provided, which serves to effectively avoid damaging the roof structure, i.e. avoids damage both to the rafters and the heat-insulating layer.

The vapor barrier according to the present invention therefore allows the easy rehabilitation of steep-pitched roofs, wherein the vapor barrier is wrapped in an easy manner around the rafters in a loop and laid across the space between rafters. The vapor barrier according to the present invention is not limited, however, to the use in the case of a roof rehabilitation but can also be used for the rehabilitation of half-timbered structures or also for the new construction of steep-pitched roofs or for wooden post-and-beam structures for exterior walls, wherein the advantage lies in that humidity or new building humidity introduced in the half-timbered structure, and new building humidity in the steep-pitched roof dries more quickly.

The vapor barrier according to the present invention can be manufactured in a particularly cost-effective way and therefore contributes to the reduction of the overall rehabilitation cost when it is used as a rehabilitation vapor barrier. According to an advantageous embodiment of the invention, the vapor barrier has a constant s_(d) factor in the range between 0.6 and 1,7 m, advantageously in the range between 0.8 and 1.6 m, in particular in the range between 1 and 1.5 m. In the case where the vapor barrier is used for rehabilitation, this range ensures sufficient water vapor permeability in the area of the rafters in a particularly reliable manner, so that it is ensured that the timber moisture never exceeds the critical value of 18%. At the same time, the diffusion resistance of the vapor barrier in the area of the space between rafters is sufficiently high to avoid the formation of condensate within the roof structure, in particular on the underside of a roof underlay to be arranged on a steep-pitched roof.

In principle, the vapor barrier can be manufactured from any suitable material and can have one layer or may be multi-layer. In addition to the always present functional layer, which alone can form the vapor barrier, the vapor barrier may also be formed by a combination of a reinforcing layer with the functional layer to improve the mechanical properties of the vapor barrier. As an alternative, it is also possible to embed the reinforcement into the functional layer, wherein both the reinforcing layer and the embedded reinforcements can be used to adjust the s_(d) factor of the vapor barrier.

The s_(d) factor of the vapor barrier primarily depends on the material used to manufacture it. The s_(d) factor can also be adjusted, for example, by the use of additives, such as suitable fillers or fibers, by certain manufacturing methods, such as partial stretching, or by adjusting a suitable porosity in a simple manner. The materials can be special paper materials, modified papers, or the like. The necessary porosity can also be provided by purely fibrous products which can be double-calendared, if necessary.

According to an advantageous embodiment of the present invention, the vapor barrier, however, comprises a plastic foil which can be particularly easily and cheaply manufactured. The vapor barrier modified in this manner may, for example, be extruded or manufactured by extrusion coating. The vapor barrier may also be manufactured by adhesively gluing individual layers, by the brush application of pastes, for example, by roller coating, spraying or calendaring.

The plastic materials may be materials which enable the vapor barrier to be manufactured with the features according to the present invention. Polyethylene copolymers, polycarbonates or polyvinyl chlorides are suitable, for example. According to another embodiment of the present invention, the plastic foil is manufactured of modified polyethylene, particularly advantageously of an ethylene vinyl acetate copolymer, in an extrusion process. These materials enable the vapor barrier which, at the same time, is particularly rugged with respect to external influences, to be manufactured in a particularly cost-effective manner.

In the application case, the vapor barrier according to the present invention, which may be supplied in the form of foil, sheet, textile, non-woven material or the like, can be installed with particular ease. This feature is additionally improved according to an advantageous embodiment in such a way that the vapor barrier is flexible, foldable and/or rollable. An attendant improvement in the installation of the vapor barrier is provided according to another advantageous embodiment of the present invention, wherein the vapor barrier is partially self-adhesive, in particular comprises a self-adhesive edge area. This particularly facilitates bonding on the rafters or an existing interior cladding in the case where the vapor barrier is used for rehabilitation. Also, bonding of adjacent vapor barriers can be considerably facilitated in the overlapping areas.

To improve its ruggedness, the vapor barrier can be advantageously provided with reinforcements, in particular formed by a grid, a textile, a laying, knitwear and/or a non-woven structure. The reinforcement can also be formed by fibers or filaments embedded in the vapor barrier. The reinforcement is for additionally improving the tear resistance or tear propagation resistance of the vapor barrier and also obviates damage due to punctures. Herein the reinforcement is embedded in the vapor barrier.

According to another embodiment of the present invention, the vapor barrier can also be applied to a carrier layer, which is advantageously a textile, a tufted material or a thermally reinforced non-woven material. In addition to the mechanical reinforcement of the vapor barrier by means of the carrier layer, the latter may also fulfill functional properties and so additionally improve the applicability of the vapor barrier. According to this embodiment of the invention, the vapor barrier is advantageously manufactured by extruding the plastic foil onto the selected carrier layer.

According to another embodiment of the present invention, the vapor barrier comprises additives, such as for determining its color, its fire behavior and/or its resistance to ageing. To achieve this, for example, suitable stabilizers (e.g. UV or thermal stabilizers), colorants and color pigments, flame retardants and other fillers or filling fibers may be used. The addition of additives according to this embodiment of the invention enables the vapor barrier to be optimally adjusted to the intended application.

An exemplary embodiment will be described in the following with reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a roof structure on which a vapor barrier extends across two rafters and the adjacent space between rafters, and

FIG. 2 is a cross-sectional view of the roof structure of FIG. 1, wherein the insulation is installed and the roof underlay arranged on it.

FIG. 1 shows a portion of a cross-section of a roof structure 1 with two neighboring rafters 2 and a space between rafters 2. From the inside of the roof structure, an interior cladding 4 with a decorative layer 5 applied to it is arranged on rafters 2, wherein interior cladding 4 is directly adjacent to rafters 2. On top of rafters 2, and on the exterior surfaces of interior cladding 4 facing rafters 2, for rehabilitation purposes a vapor barrier 3 is wrapped round the outside and lateral surfaces of rafters 2 in a loop and extends in the area of the space between rafters on the exterior surface of interior cladding 4.

Vapor barrier 3 is an extruded foil having a weight per unit area of 52 g/m² according to the following formula: 89% of an ethylene vinyl acetate copolymer with a percentage of 28% vinyl acetate, 4% carbon pigment batch on the basis of LDPE with a percentage of 50% carbon and 7% flame retardant batch on the basis of LDPE with 70% active substance (a mixture of chloro-paraffins and antimony trioxide).

In the case of the rehabilitation of the roof of an old building, vapor barrier 3 is installed after removing the roof covering (not shown) and any existing insulation. Herein, vapor barrier 3 is installed in such a way that existing interior cladding 4 is not destroyed.

During the further rehabilitation work, as can be seen in FIG. 2, an insulation 7 is inserted in the space between the rafters, and a roof underlay 6 is applied on the outside of the rafters, on which the roof covering (not shown) can then be installed.

Vapor barrier 3 shown here has an s_(d) factor of 1.25 m, which ensures that the timber moisture due to water vapor diffusion in the area of rafters 2 does not exceed 18% at any time wherein, at the same time, condensate is not formed in the area of heat insulation 7, which could lead to a considerable reduction of the insulating performance of heat insulation 7.

The vapor barrier can be manufactured by a coating with a weight per unit area of 21 g/m², namely by partially adhesively gluing a previously extruded foil on a carrier web.

Four further embodiments of the vapor barrier according to the present invention are shown below in table 1 wherein the water vapor permeability, the weight per unit area and the s_(d) factor (according to DIN 52615, 23° C., o/85% relative humidity) are shown. These vapor barriers can be manufactured by extrusion coating with a thermally point-reinforced polypropylene spun-bonded non-woven (weight per unit area of 40 g/m²).

TABLE 1 Weight per unit area water vapor s_(d) overall weight of the coating permeability factor per unit area g/m² g/m²d m g/m² 76 21 1.9 116 50 32 1.25 90 33 54 0.74 73 21 100 0.4 61 

1. A vapor barrier for use in buildings, characterized in that it has a water vapor diffusion resistance (s_(d) factor) of 0.4 to 1.9 m diffusion-equivalent air layer thickness which is constant over the entire surface area.
 2. The vapor barrier according to claim 1, characterized in that it has a constant s_(d) factor of 0.6 to 1.7 m.
 3. The vapor barrier according to claim 1, characterized in that it comprises a plastic foil.
 4. The vapor barrier according to claim 1, characterized in that the plastic foil is manufactured with an extrusion process.
 5. The vapor barrier according to claim 1, characterized in that the plastic foil is of a modified polyethylene.
 6. The vapor barrier according to claim 1, characterized in that the plastic foil is of an ethylene vinyl acetate copolymer.
 7. The vapor barrier according to claim 1, characterized in that it is flexible, foldable and/or rollable.
 8. The vapor barrier according to claim 1, characterized in that it is partially self-adhesive.
 9. The vapor barrier according to claim 1, characterized in that it has a self-adhesive edge area.
 10. The vapor barrier according to claim 1, characterized in that it has a reinforcement.
 11. The vapor barrier according to claim 1, characterized in that the reinforcement is of selected from the group consisting of a textile, a laying, knitwear a non-woven material and combinations thereof.
 12. The vapor barrier according to claim 1, characterized in that it comprises a carrier layer.
 13. The vapor barrier according to claim 1, characterized in that the carrier layer is of a textile or a non-woven material.
 14. The vapor barrier according to claim 1, characterized in that it comprises additives to determine at least one of its color, its fire behavior its resistance to ageing.
 15. The vapor barrier according to claim 1, wherein the barrier is in a facade or a roof.
 16. The vapor barrier according to claim 2, wherein the barrier has a constant s_(d) factor of 0.8 to 1.6 m.
 17. The vapor barrier according to claim 2, wherein the barrier has a constant s_(d) factor of 1.0 to 1.5 m.
 18. The vapor barrier according to claim 13, wherein the carrier layer is of a tufted material or thermally reinforced non-woven material. 